The present invention relates to a conveyor having self-propelled carriers, for example, for use in motor vehicle production lines.
With motor vehicle production lines, a plurality of carriers having vehicle parts (article to be transported) placed thereon need to be moved through a specified work zone with a constant distance maintained between the carriers. Accordingly, power-and-free trolley conveyors have heretofore been used.
However, the power-and-free trolley conveyor employs chains and therefore has the problem of giving off a great noise and being unable to drive the carriers at a high speed in transport zones or the like other than the work zone. Furthermore, it is extremely difficult to alter the carrier-to-carrier distance which has been determined.
Accordingly, conveyors having a plurality of self-propelled carriers have been proposed to ensure a reduced noise and to drive the carriers at a higher speed.
Nevertheless, the conveyor of this type has the problem that it is difficult to maintain a constant distance between the carriers in the work zone since the carriers are caused to run independently of one another as by electric motors.
These problems may be overcome by installing a conveyor with self-propelled carriers in the transport zone and a power-and-free conveyor in the work zone, and transferring the articles to be transported from one of the conveyors to the other conveyor, whereas the transfer procedure is cumbersome, and the line becomes difficult to alter or modify.
Alternatively, it appears feasible to install the conveyor with self-propelled carriers for the entire line and to use a chain for moving the self-propelled carriers in the work zone. However, the work zone then requires the two types of conveyors, which also makes the line difficult to alter.